We have a new cable box/DVR, and the display is too bright. How can I dim it? Suggestions found on the web, to put a piece of tinted tape over it, are unsatisfying.
I have an older DCT series Motorola box, and there’s no way I can find to do it. the couple of DCX series ones I’ve put hands on seem to be the same.
For single LEDs, I’ll cover them with regular scotch tape, then colour it over with a Sharpie until it reaches the desired brightness. Kinda close to your original solution, but… 
You can use a bit of a post-it as well. Then after a week, switch to Nanoda’s suggestion, and it will look positively classy.
If you want to do it in the most professional way possible, you could replace the resistors that drive the display elements with higher value ones. This will cause the current feeding the display (and consecutively the light intensity) to drop.
I found a photo of the device and it looks like it uses a typical 7-segment display so all you have to replace is 7 resistors, maybe a few more if there are some extra elements.